Anna had her hearing tested when she was one day old.
They mounted electrodes on her head and neck, put on some fancy headphones and then played noises and measured through the electrodes whether her brain registered them. She was asleep half the time, but it still worked fine (and her hearing was just fine, by the way).
I think it’s so much better to measure it electronically and at an early age. In Denmark, they seemingly still do it the old-fashioned way, and it’s just not nearly as precise.
For instance, what happened when my niece Ursula had her hearing test at eight months was this: The nurse stood behind her and made a noise to the left. Ursula turned her head and looked at her. She then made a similar noise to the right, but this time Ursula had figured out what was happening, so she didn’t bother doing looking, and the nurse therefore thought she was deaf in her right ear. It took weeks till she got a proper test and established that their was nothing wrong with her hearing in the first instance.